Tilley's Hiker's Hat is powered by HyperKewl™ which limits heat stress on long hikes with its evaporative cooling insert. One may secure the hat when not worn using its rear brim loop. All this includes Tilley's usual array of features making for impressive headwear.Features:HyperKewl™ evaporative cooling material absorbs & slowly releases water through evaporation to help 'supercharge' the body’s natural cooling process.Certified UPF 50+ (the highest given).Broad brim protects from both sun & rain.3/4" mesh insert around the top provides additional ventilation.Front & back wind cords system secures it in gusty conditions.Rear brim loop provides a place to clip it in place securely.Water-repellent finish keeps off the rain of it.Mesh pocket in crown holds the insert.Stays afloat on water.Made in CanadaMaterial:93% breathable nylon.7% spandex.The fabrics of all Tilley Hats have been certified to block 98% of harmful UVA/UVB radiation and deliver an ultraviolet factor (UPF) of 50+, the maximum rating given.Brim Measurements (Size 7 3/8):- Front: 2 5/8"- Back: 2 3/4"- Sides: 2 1/8"Size Assistance:54.5 cm = 6 7/855.5 cm = 756.5 cms = 7 1/8 - Average womans size *57.5 cms = 7 1/458.5 cms = 7 3/8 - Average mens size59.5 cms = 7 1/260.5 cms = 7 5/861.5 cms = 7 3/4 *62.5 cms = 7 7/863.5 cms = 864.5 cms = 8 +Care:Wash it frequently or non-removable sweat stains will mar it and possibly rot it. Machine wash on delicate cycle separately or hand wash in cool water. Do not use bleach as it remains inside the Hat, slowly rotting it. Smooth and reshape the Hat by hand and set it out to air dry. When the Hat is dry, simply re-stretch it, as an American sailor showed, by putting your knee in the crown, and pulling firmly on the opposite side. Tilley T4MO Hikers Hat | Grey